Thyroid UK
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Blood Tests


I am booked in for some blood tests to check my thyroid levels. After years of managing fine on 75 mcg of thyroxine I've developed other symptoms now of extreme tiredness, anxiety, not being able to sleep, pain in my hands ...the list goes on.

My first question is can this happen over time and secondly I'm booked in for my bloods in the afternoon and usually take my thyroxine in the morning = should i wait until after my bloods before taking my daily dosage?

Many thanks for any advice


6 Replies

Hi mrsknibb, you do know that your TSH will be much lower in the afternoon than it will in the morning, don't you? Does your doctor just go by TSH? If so, s/he could possibly conclude that you need a reduction in dose, when in fact you need an increase. What time do you normally have your tests? It's best to always have them at the same time of day, or you cannot compare them. Would it not be possible to cancel this appointment, and make another one, earlier - like before 9.0 am.

You should leave a 24 hour gap between your last dose of levo, and your test. So, if you don't take it that morning, that will give you too long a gap. But if you do take it, the gap won't be long enough, and you will, in part, just be testing what you last took, rather than what would normally be in the blood. Another good reason for having your blood test early morning.

And, for your other question, yes, it can happen. And I'm surprised it hasn't happened sooner, because 75 mcg is not much more than a starter dose. So, you really do need to have your test under ideal conditions.

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Many thanks for getting back to me - no wonder i feel rubbish - my tests have always happened like this. I've cancelled my appointment and made one for first thing in the morning.


:) So, fast over-night - just drink water, because eating lowers the TSH - and leave a 24 hour gap between your last dose and the test. Good luck!

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One doctor was forever complaining to the Endocrinology Associations that the doses of thyroid hormone given to patients was too 'low' nowadays as it used to be around 200 to 400mcg before blood tests were introduced.

I am surprised too that you've been on 75mcg for so long and the response by Greygoose is correct. In order to get the 'best result' from blood tests for thyroid hormones as many doctors only take notice of the TSH (which drops throughout the day) the test should be the very earliest possible and about 24 hours gap between your last dose of levo and the test. Also ask for B12, Vit D, iron, ferritin and folate too.


Thank you - and yes the doctor i saw is new and she suggested i have the other things you mentioned tested. I think i will come back on here with all my results to see if what the doctor advises based on my results matches up with your advice

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That's good as we need a thorough blood test each time and the main problem is that the Endocrinology (BTA) say that they have to go by the TSH alone. That why we, the patients, have severe problems as we are usually underdosed to keep the TSH in range.

Usually when blood tests are requested some labs only do the TSH and if in range they don't do the others. We do have the facility of recommended labs and you get a small discount.


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